There are many types of ballast circuits for energizing devices that emit visible light, such as fluorescent lamps. A so-called electronic ballast receives a relatively low frequency AC (Alternating Current) input signal and provides a relatively high frequency AC output signal to one or more lamps. Typically, the low frequency input signal corresponds to a standard 110 volt, 60 Hz signal which is selectively applied to the ballast by means of a conventional wall switch.
One type of electronic ballast includes a rectifier which receives the AC input signal and provides a DC (Direct Current) signal to an inverter. The inverter can be a resonant inverter which provides a relatively high frequency AC signal to the lamps at operational voltage and current levels which cause the lamps to emit light.
Generally, the ballast is coupled to a source of AC energy via a switch, for example a conventional wall switch, which controls the flow of energy to the ballast for turning the lamps on and off. That is, when the switch is set to an on position the AC signal is applied to the ballast which energizes the lamps such that they emit light. And when the switch is set to an off position, the AC signal is not applied to the ballast and the lamps do not emit light. However, conventional ballasts are not adapted for coupling to more than one AC input signal and do not provide independent control over multiple lamps coupled to the ballast.
It would, therefore, be desirable to provide a ballast circuit adapted for receiving more than one AC input signal and independently controlling a plurality of lamps coupled to the ballast.